Bundle of His electrograms in congenital corrected transposition of the great arteries. A study of two adult cases.

His bundle electrograms were recorded in 2 adult cases of congenital corrected transposition of the great arteries.Both patients had prolonged HV conduction and a His potential that was wide.These findings are different from those reported in congenital atrioventricular block without ventricular inversion wherein an abnormality within the AHperiod has been found.It is suggested that these differences reflect different sites of disturbed conduction.In congenital corrected transposition of the great vessels, the abnormality is distal to the atrioventricular node, whereas in congenital atrioventricular block without ventricular inversion it is generally proximal to the atrioventricular node.His bundle electrocardiography has been used to localize the site of conduction disturbance in atrio- ventricular block (Damato et al., I969; Narula et al., I970a).Atrioventricular conduction abnormalities have been found in more than one-third of reported cases of congenital corrected transposition of the great arteries (Friedberg and Nadas, I970).To de- termine the site of disturbance in 2 adult cases of congenital corrected transposition of the great arteries, His bundle electrocardiography was performed.The results of these studies are now re- ported and discussed in the light of previous mor- phological and electrophysiological studies. MethodsPatients were studied at the time of routine cardiac catheterization.Diazepam was administered one hour before oatheterization and approximately 3 hours before His bundle electrograms were obtained.One patient (Case 2) had been receiving digoxin 0-25 mg each day; it was stopped 72 hours before study.No other drugs were administered during the preceding two weeks.His bundle electrograms were recorded using the method described by Scherlag et al. (I969).Specifically, a multipolar catheter was advanced via a femoral vein across the right-sided antrioventricular (mitral) valve.His bundle electrograms and simultaneous surface electrocardiograms were recorded at a paper speed of 200 mm/sec on a multichannel recorder (Electronics for Medicine -DR-I2).